For those (like me) who cant multiply by 25.4 in their head I have modified the speeds and feeds chart from Carbide to include metric as well as imperial. It is in the form of an excel spreadsheet - if anyone wants it in another format please let me know. Alex PDF now attached
I haven't been that brave yet - the table is for a 1/4" cutter. I usually use a 1/8" or 3mm cutter and my maximum depth of cut is about 3mm, so I suppose it sounds about right for 1/4". I would be inclined to experiment with different DOC's - if it sounds as though the cutter is being strained or you see signs of the cutter being pushed sideways you are going too far.The table also doesn't state how many flutes the cutter has. The DOC you can achieve also depends on how rigid your machine is - the more flex in your framework the less DOC you can manage. Having said that you should be aiming to cut chips rather than dust - too high spindle speed, low feed rate and low DOC means the cutter will be rubbing against the material instead of cutting = heat = blunt tool. The table is only a guide to get you started - experiment on scrap with different spindle speeds and feed rates and about half the DOC the table suggests until you feel the cutter is working efficiently and then increase the DOC until you see signs of strain - then back off a bit. The workbee is a pretty tough machine - I once stupidly hit a clamp on the bed and it ripped the 18mm mdf spoiler board apart. (I don't recommend trying this). Alex.
By the way, I just cut acrylic with a 1/4 inch Onsrud O flute endmill with a Makita and those settings worked very well.
Hi Alex, Thanks for the sheet it'll make my life easier to start testing materials. One question though - DOC stands for....? and 'feed' is your cutting feedrate/min? Also regarding plastics, I'm finding HIPS extremely difficult to cut (melts, foams, and wherever it cuts foam reforms behind to mess up the cut. I rarely get a neat cut, plastic sticks to drill bit and hardens while working). I know you use Fusion 360 so was wondering if you also play with conventional vs climb rotation. I've already realised a single flute is the best, and multiple depth of big max 2mm per pass so that's a start....(if your experience says otherwise let me know!)! Do you have an other tips for plastics in general and especially HIPS? For sure I need to invest in some blower/cooling system. Thanks! Heba
DOC = depth of cut. I have a Makita (Chinese clone) so use slowest speed (10,000 rpm) for HIPS and would go slower if I could. Feed is feedrate / min. I can't remember what that table recommended for HIPS - I use the fastest I can (about 2,000 mm/min) I have been using a 4 flute upcutter 3mm end mill with some success, I did use 20 degree single flute engraving bits but found melting was a problem. Cooling fan sounds like a good idea. For softer materials I prefer to use conventional milling. Alex.
PS - my experience with cnc routers is measured in months, not years - do post your own results here.
I will take good notes for my next tests and will try with both one flute and four flute (would never have thought of using a four flute!!) and post my results here foe sure. Thanks again for your help!
I just did the imperial/metric conversion sums on the chart from carbide which was for a 1/4" bit, but I don't think it even said what sort of bit. Alex.
So, do you think its based on full woc? I've only been cutting plywood and plastic. I want to cut out some walnut this weekend using adaptive so WOC is important.
Can't answer that @sharmstr, but from my experience of machining mahogany (which they give figures for) I would say that the term "mahogany" covers a wide range of species and some very different properties so that table can only be regarded as a rough guide. Alex. PS the original chart is here; Materials Speeds and Feeds Chart
For hard woods, I like to use a two straight flute endmill to prevent tear out. I have had good luck in oak cutting depth of 1/2 the diameter at 2500 mm per minute. Here is an 1/8 inch bit that I use with both woods and plastics. I always ramp in to the material with these bits. https://www.amazon.com/Straight-EnP...e&qid=1561738653&s=gateway&sr=8-2-spons&psc=1 I have a 1/4 Freud 2 flute similar to the one in the link that I love. The one in the link I own as well and love it. Also, I use a dust collector when using these bits and it clears the chips out well.
I haven't worked American (black) walnut and only used hand tools on European walnut although I believe they are very similar to work. How they behave depends on the grain - straight grain little problem - figured grain tearout can be a problem. I found this link if it's any help. Wood Species Guide Alex. PS wear a dust mask.
Regarding the cooling fan, I tend to have a vac nozzle really close to the bit - sucking cold air past it - same effect. Alex.
Sorry I missed this. I have been on vacation in areas with limited cell phone reception and no wifi. I highly recommend it. I have been using the same speeds an feeds just deeper cuts (1/2 diameter) with the 1/4 inch.
Thanks for preparing this, Alex! As a new CNC router owner I need all the help I can get! I was looking at this spreadsheet and I thought I would modify it a bit for my own use. One thing led to another and I added a few things. The main thing is it now provides an alternate calculation for feeds. If values are entered in the blue cells, the cutting parameters are calculated. Maybe something in this would be of interest, or helpful, to others. Some items of note: The depth of cut (as a fraction of tool diameter) and the chip load values from the Carbide 3D data are calculated and highlighted in grey. This can be compared to data for similar materials from other sources. The ROUTER RPM worksheet derives equations for calculating the router speed settings from the speed setting tables Rounding is applied where I thought it made sense. Suggestions for corrections and improvements are welcome. I make no guarantees for validity of correctness. Use at your own risk!
That's impressive @rscamp ! Can I suggest something I must do to the chart I posted? - carbon fibre should be labelled as dangerous (it was on the original carbide chart - I overlooked that when typing it into excel) Alex.
Thanks for the head's up. I see the skull and crossbones on the original chart but I don't see a description of the health hazard. I can find articles like this online so the risk appears to be not unlike that for asbestos. I think there are health concerns related to the airborne particulates/fibers for all of the materials we cut. Maybe a general warning is more important? I added some cautionary notes...
Thanks for the table Alex. I just run some plywood yesterday at 2000mm per minute, number 3 with a Dewalt router, 2mm DOC and got some terrible chip out and burring! With a brand new bit too. I'll see if increasing my cut speed or DOC make things any better.
I prefer two flute/straight flute endmills for wood. They cut clean and do not chip out. This one has worked well for me, but is slightly undersized (6.28mm rather than 6.35).
I've not been able to find a bit like this that's 1/4 either in the UK. I have ordered a 1/8 and a reducer. The bit has arrived and it's tiny! I'm a little bit worried it'll snap. I have found them in 6mm [this might be 6.28mm when measured] and 8mm bits though, so if this 1/8 bit cuts cleanly I could always get a different size collet for those if I left the need to. We'll just have to wait and see. =)
For wood you could use a 1/4" shank router bit. They don't always plunge well though - they often have a "dead" section in the centre - use ramp in at the start of cuts. Alex.
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